The present invention relates to no-relight cigar lighter sockets.
There is increasing use today in automobiles of plastic dashboards. Plastic dashboards can suffer distortion and damage due to excess of temperatures above about 200.degree. F.
Conventional cigar lighters employ a clamping device of bimetal material in the socket into which the burner cup is pressed and the burner cup is retained there and fed electrical current by the clamp members. When the heater element in the burner cup reaches a predetermined temperature, the bimetallic clamp members relax to release the burner cup and the burner cup is partially retracted by a spring. Movement of the burner cup alerts the operator to the fact that the lighter is ready for use.
Some impatient users of cigar lighters attempt to excessively heat the burner by holding the burner cup into the clamp members for longer than would be permitted by the bimetallic elements. This can increase the temperature of the burner and burner cup to very high values. In fact, it is not uncommon to actually melt metallic parts of a cigar lighter from such use when continued for a long time. Overheating of the cigar lighter on this scale is far beyond the permissible temperature for plastic dashboards.
The continuous overheating just described is most severe in prior art cigar lighters which have metallic stops to limit the inward penetration of the burner cup. These metallic stops are usually connected to the same electrical source as are the bimetallic clamps. Consequently, pushing in on the cigar lighter establishes an energization circuit through the stop as well as through the bimetallic clamps.
One approach to reducing the severity of overheating in prior art cigar lighters is taught in U.S. Pat. No. 3,887,789, herein incorporated by reference, in which the surfaces of the mechanical stop which are abutted by the burner cup are coated with an insulating high temperature ceramic material. The insulating ceramic coating prevents the feeding of current to the burner through the mechanical stop. This prior art patent, however, still permits the bimetallic clamp elements to contact the sides of the burner cup when the cigar lighter is pressed fully into the socket. As the burner cup heats up, the bimetallic clamp elements loosen their contact with the burner cup and, when hot enough, are moved at least partially out of contact therewith. Manufacturing tolerances, however, make it common for good electrical contact to continue on one or both of the bimetal clamping members on the burner cup to temperatures well above the damage point of plastic dashboards.